The Amounts of Nitrogen as Ammonia and as Nitric Acid, and of Chlorine in the Rain-water collected at Rothamsted.

At the time of the commencement of the Rothamsted experiments very little was known as to the amounts of combined nitrogen and other substances present in rain-water. Marggraf (74) found nitric acid, chlorine and lime in rain-water collected during the winter of 1749–50, and, subsequently, in snow. These analyses, which are probably the earliest, were followed by those of Bergman (15) who detected the same substances both in rain and snow; whilst somewhat later de Saussure (99) noticed the presence of ammonia in the atmosphere. Between 1820 and 1825 several analyses of rain-water were made.